Re mortgage deduction... my inlaws pay the mortage on the house we share...we pay them our share. we are legally "50% tenant in common"...how do I get our deduction?

In TurboTax, you can enter your portion of mortgage interest paid by following the interview questions.

Go to Federal Taxes > Deductions & Credits > Your Home > Mortgage Interest

In the interview, you'll see a page titled  Do any of these uncommon situations apply to your loan with Bank? (see screenshot 1). Answer the questions and click Continue

On the next page, you enter the details of the person whose name appears on the form 1098 (see screenshot 2).

Continue the interview to enter your portion of the mortgage interest.